The invention relates to a method of using nano-sized iron oxide to induce the surface of carbon steel through nitrogen alloying. The method mainly comprises the following steps: (1) preparing nano-sized iron oxide: preparing 0.1mol/L of ferric nitrate solution, slowly dropping 1.0mol/L of ammonia under vigorous stirring of a magnetic stirrer; after complete precipitation of iron ions, using a centrifuge to separate the precipitate, cleaning with distilled water, drying, roasting in a muffle furnace at 350 DEG C for 4h; (2) using the prepared nano-sized iron oxide to perform ultrasonic dispersion according to the content of 10-40g/L in ethanol solution, spraying the obtained solution on the surface of carbon steel, wherein the thickness of the coating is controlled to 600nm-2mu m; and (3)placing the carbon steel with nano-sized iron oxide, obtained by the above method in a fixed bed quartz tube reactor, standing at 500 DEG C for 2h under pure ammonia atmosphere, cooling the obtained carbon steel along with the furnace to the room temperature; and introducing a mixture gas of O2 and N2 in the reaction tube under room temperature to perform surface passivation treatment, wherein the volume percent of O2 to N2 is 0.6%;and finally obtaining the carbon steel of which surface is through nitrogen alloying. The surface of the carbon steel is dark gray, is a flat or even surface and has good corrosion resistance and higher hardness.